Miniature lamp



Dec. 13, 1966 w` scHlLLlNG ETAL 3,290,906

MINIATURE LAMP 3 Sheets-Sheet i1 Filed July e, 1954 FIG. 1

FIG. 3

Dec. 13, 19.66 vv.sc;H1L.L.xNG ET AL 3,290,906

I Mmmm: LAMP Filed July 6, 1964 5 Sheets-Sheet 2 FIG. 5

WERNER SCHILUNG HANS WIEDENMANN ,INVENTORS BV ATT MEY Dec. 13, 1966 W` scHlLLxNG ET AL L MINIATURE LAMP Filed July 6, 1964 5 Sheets-Sheet 3 FIG. 10

FIG.1OA

WERNER SCHlLLlNG HANS WlEDENMANN INVENTORS BY ATT RNEY United States Patent O 3,299,906 MEINIATURE L Werner Schilling and Hans Wiedenmann, Heidenheim (Brenz), Germany, assignors to Patent-Treuhand-Gesellschaft fur Elektrische Glulilampen nihil., Munich, Germany, a corporation of Germany Filed July 6, 1964, Ser. No. 380,208 Claims priority, application Germany, Ililly 16, 1963, l? 32,2113 Claims. (Cl. 67--3]l) The present invention relates to a miniature lamp with flattened pinch in which the flattened pinch constitutes the lamp base. A usual comparative photoflash lamp consists of a piece of glass tubing at one end of which is provided a flattened pinch constituting the lamp base and at the other end of the formed lamp is located a tip-seal. The in-leads are sealed where passing through the flattened pinch. Since the exhaust tip-seal of the well-known lamp is located at the end of the lamp opposite from the flattened pinch, it poses difficulties and restrictions. For instance, a lamp thus made, `has a useless extra length resultant from the presence of this exhaust tip which projects at the lamp end, but which docs not increase the effective bulb volume by the increase of over-all length.

Broadly, therefore, it is an object of the present invention to provide a miniature lamp utilizing a flattened pinch serving also in the capacity of base for the lamp, but in Which an exhaust tubulation is utilized and is located in the pinch or base end of the lamp.

Also the invention proposes a lamp constructed in its entirety so as to require a pinch only of minimum width and thickness without imposing undue restrictions in shaping the pinch to also constitute a glass base and at the same time making it possible to choose the bulb shape and size without having to contend with an exhaust tip or with a bulky glass tabulation.

Prior art has proposed a miniature lamp provided with a flattened pinch in which is located an exhaust tubulation of glass. From a practical standpoint, there is a minimum of diameter for the passageway of the exhaust tubulation, and also a minimum wall thickness of the tubulation necessary for strength, not only for resisting breakage in handling, but to resist heat and compression during installation. Due to the necessary comparatively large outer diameter of glass tubulation for miniature lamps, shaping of the pinch is restricted; for instance, to use an acceptable size of glass tubulation in a miniature lamp it is impossible to make the pinch thin enough to function as a base with required depth of grooves transverse to the lamp axis at the ilat faces of the pinch, such grooves being desirable for magazine loading and use.

According to the present invention, a miniature photoilash lamp is provided utilizing minimum thickness of flattened pinch, characterized by utilization of a thinwalled metallic tubulation, preferably copper, which will maintain full-diameter passageway therethrough during formation of the pinch and transverse grooves in the pinch passing close to the tubulation.

Heretofore it has been deemed necessary for obtaining a tight seal of glass to copper, that only certain kinds of glass, more particular hard glass only, could be used. For the manufacture of competitively cheap mass-production items, such as photo-flash lamps, available hard glasses are so expensive as to make use thereof prohibitive.

Much to our surprise, we have discovered that soft glass lamp stock, heretofore used only with glass tubulations, may be sealed or pinched with gas-tight effectiveness on thin copper tubulations. Glasses of this character which we have proved acceptable are those identified ice in the trade as lead glasses and lime-magnesia glasses.

For the purpose of making a durable tight seal, the outer diameter of the copper tubulation must be as small as or smaller than 1.5 mm. and the wall thickness of the copper tubulation must not exceed 0.2 mm. Copper tubulations having an outer diameter of 0.8 mm. and a wall thickness of 0.1 mm. have functioned perfectly and are preferred. For the successful practice of the invention, semi-hard copper tubing has to be used, as the seal may not be satisfactorily effective when either hard or soft copper tubing is used. By semi-hard copper is meant copper that has been formed or processed, as by cold-rolling or cold-drawing, to one and a half times the tensile strength of soft copper made by annealing.

The invention is even more unique, in that the soft glasses mentioned above as scalable to thin copper tubing of sizes within the stated range, will not seal to a solid copper wire even of the preferred dimension of 0.8 mm. The discovery of the unexpected fact that a seal may be made to the thin tubular metal where such glass could not be sealed to solid wire is of great importance in enabling a much improved miniature lamp to be made.

In prior art manufacture of lamps wherein glass tubulation cannot be employed due to its excessive diameter, the pinch is made after the in-leads have been positioned, thereby closing that end of the envelope, the other end still being open but tip-sealed after the envelope has been gas filled. The technique of providing a lamp with high gas pressure is to introduce the gas in liquid form in appropriate amount through the open end of the envelope, and after tip-sealing the envelope to then let the liquid gas return to gaseous form. Until the lamp is sealed-off, therefore, the liquid gas therein must be kept cold to remain liquid. This mode of producing a superpressure filling has been accomplished by maintaining the closed end of the bulb dipped in liquid nitrogen with the unsealed end protruding above the liquid nitrogen surface and the gas lilling then introduced and is so much condensed or even partially liquied that a low pressure prevails in the lamp, and while in that condition, the lamp is sealed olf with its tip seal. In addition to the fact that this method is effective, the use of heat to sealod the lamp greatly adds to the consumption of the liquid nitrogen and therefore is proportionately expensive. This presents an even greater problem of inefficiency with miniature lamps due to their small dimensions which brings the sealing or tipping-off heat in exceedingly close proximity to the nitrogen surface which is thereby rapidly vaporized. The miniature lamps here referred to have a total length of about 32 mm. only, and since about 7 mm. are utilized in forming the pinch, the center of the bulb being cooled lies only about 12.5 mm. remote from the sealed-off area. This short distance between that part of the glass taking the temperature of the liquid nitrogen and that part of the glass being brought to high temperature for the purpose of sealing-olf, introduces an extremely serious problem prohibitive to economical manufacture of miniature lamps by this method without considerable technical expenditure. The lamp dimensions given represent normal minimum size of lamps currently available and too small for manufacture with use of glass tubulation, whereas, according to the present invention the objective is attained of capability of fabricating even smaller lamps with use of tubulation.

It could not be anticipated that a metallic tube could accomplish an effective seal for an envelope filled with gas at high pressure by simple mechanical pinching and cold welding of the tube. However, we have discovered that the pinch produced in thin-wall copper tubes utilized in the lamps of the present invention are extremely pressureproof and very stable. As a precaution, or for other desired reason, the pinch of the metallic tubulation used in this invention, may be doubly sealed by an encasiug coating, such as solder, rigid plastic, lacquer or other suitable material, either singly or as a laminated coating of different ones of said materials. Use of such coatings also serves both as protection and reenforcernent for the thinwall metallic tubing.

By utilization of the present invention, we attain the objective of mass production of miniature lamps having superpressure gas lling whereby said lamps can be fabricated on high-speed rotary machines with sealing effected at the same end at which the in-lead wires and tubulation are located and Without any objectionable tipolf being required at the opposite end of the lamp, thereby shortening the lamp and enabling its outer end to be rounded for greater strength and better light-transmission thereat.

The invention also accomplishes the essential object of eliminating necessity and expense of use of liquid nitrogen, but permits direct introduction of the gas filling at desired pressure and permanently retains the gas in the lamp by cold fusion sealing of `a metallic tubulation by a very forceful pinching of the tubulation and severing the same below the pinch.

Amongst other objects of the invention may be mentioned the provision of a lamp offering a wide latitude of choice of shape thereof not only as to desired shortness or over-all length, but also both as to diameter of the bulb and dimension of the base-forming pinch of the glass. From what has already been said above, it will be recognized that the stem pinch possible with miniature bulbs of 12 mm. diameter if glass tubulation were used Would be limited to a greater thickness than we attain, since a glass tubulation must of necessity have a greater outer diameter than with a thin-wall metal tube, and that greater diameter of tubulation interferes with proper closeness to each other of the basal grooves in opposite faces of the pinch, such grooves being necessary for the pinch to be accommodated in standard lamp magazine holders.

Furthermore, by use of a metal tubulation, since the same is electrically conductive, the tubulation may also be employed as an in-lead, thereby avoiding need for extra space for a separate in-lead Areplaced by the tubulation. It may also be advantageous to make both of the in-leads in the for-m of metallic tubulations of thin-walled character. Thereby the total cross-section of passageway to the interior of the bulb is doubled and facility for exhausting and gas-filling the bulb is increased improving and speeding the method of manufacture. By this proposal, the total cross-sectional area of the pinch is available to tubulations.

For a better understanding of the invention, reference may be had to the accompanying drawings in which like numerals of reference indicate similar parts throughout the several views, and wherein,

FIGURE 1 is an elevation of a known prior art photoflash lamp;

FIGURE 2 is a longitudinal section through a miniature photoflash lamp of the present invention as it appears in tprocess of manufacture before closing the tubulation;

FIGURE 3 is a longitudinal section taken on a plane designated by line III-III of FIG. 2;

FIGURE 4 is an elevational view of the fully fabricated lamp of FIGS. 2 and 3;

FIGURES 5-10 inclusive are elevational views looking toward broad faces of flattened pinches with tubulations and in-leads included therewith and each view representing a modification from all others; and

FIGURES 5A-10A are edge elevational views of FIGS. 5-10 respectively.

FIGURE 11 is an elevational view corresponding to the showing of lamp of FIG. 4, but showing an additional seal applied to the pinch of the tubulation; and

FIGURE 12 is a view similar to FIG. 11, but showing the additional seal applied to all of the tubulation that projects from the lamp base.

A known miniature photoiiash lamp as shown in FIG. 1, has a bulb ll and a pinch or stem press 2 shaped as a base and is filled with shredded zirconium foil 3 as well as with oxygen under high pressure. During manufacture, the bulb, already provided with the filling is dipped, together with the stem press at its bottom, into liquid nitrogen so that the gas filling is frozen or remains under a low pressure in the bulb. Thereupon the bulb is sealed olf at its top or dome, and is doing so, a protruding tip 4 is formed which undesirably increases the total length of the lamp without increasing internal lamp volume and consequently without any increase in quantity of ultimate light, the tip, in fact blocking the light to some extent.

In the miniature photoliash lamp of the present invention as shown in FIGS. 2 to 4, the reference numeral 5 denotes the bulb consisting of glass, especially a soft glass such as lead glass or magnesia glass. At the bottom end of said bulb is an integral stem pinch 6 also functioning as a glass base for the lamp, and within the bulb is finely divided combustible material 7 such as shredded zirconium foil. The photoash lamp is made from a piece of soft glass tubing the bottom end of which is pinch-sealed around current in-leads 9a and 9b carrying, at their upper ends within the bulb, igniting means 8. A thin-walled semi-hard small diameter copper tubulation It) located between and extending lengthwise of the in-leads, also extends somewhat into the bulb and projects in opposite direction somewhat out of the bottom end of the aforesaid stem pinch 6. In the pinching operation, the stem press or pinch is brought into the desired external base form and internally makes a tight seal with the in-leads and thin-walled metallic tubulation. Through the other or top and still `open end of the glass tube, the finely divided combustible material 7 is thereupon introduced and concentrated near the pinched end proximate to the igniting means il. At a place between the already closed end, (except that the tubulation is still open) and the completely open end, the glass tube is then contracted and sealed off. Since atmospheric pressure still prevails in the lamp, the glass at the aforesaid place of sealing-olf may be softened by heat and formed, as with the use of molding tools, into a closure of semi-spherical bowl or dome shape 5a without formation of a protruding tip.

Before going further, it may be here stated that in order to facilitate sealing of the glass to the thin copper tubulation, the metallic surface is cleaned, as by use of a grease solvent, prior to insertion of the tubulation into its appointed place. The cleaned surface is subjected to a reducing agent, notably hydrogen, after which it is oxidized supericially and covered with a lm of glass, borax or enamel. The copper tube is treated preferably with a suspension of equal parts of water and lead borate with about 1% of magnesium chloride. Following domeclosing of the upper end of the lamp, the interior is exhausted through the tubulation and filled with oxygen at any desired pressure. With that completed, the tubulation l0 at an outwardly projecting part thereof, is closed by means of mechanical pinching as indicated as performed at 1l in FIG. 4. This pinching is done with considerable force and obtains a pressure-proof coldfusion lor welding which has proved successful to prevent leakage up to twenty-two atmospheres, and which may, if need be, probably be used also with even higher pressures.

In spite of the fact that the seal thus formed by cold fusion or welding is very reliable, it is recommended as a precaution in all cases in which the closed end of the tubulation is exposed and thereby subject to possible damage, when handling the lamp, that the stem press as well as the exposed tubulation be provided with a reen-forcing coating as hereinbefore mentioned, of solder, plastic or other material singly or in laminations.

For using the pinch of the glass stern as a base adapted for use in standard lamp holders or magazines, grooves b, b are required transversely across the flat face of the pinch, said grooves being in direct opposition to each other and requiring a distance between contiguous groove bottoms lof 1.7 mm. This requirement can be fulfilled in the present invention as it will be remembered that the thin copper tubing has a diameter of 1.5 mm. which will enable the tubulation to pass behind both grooves without interference therewith.

A lamp with thin metallic tubulation manufactured by the method as hereinabove described shows many advantages when compared with the known lamp shown in FIG. l. Since the tip ony the lamp dome of the prior art is omitted from the lamp of the present invention, the proportion of useful lamp length to the total length becomes greater. Consequently, in comparing the old and new lamps, the novel photoash lamp is, with equal light quantity, shorter than the prior art one, or its light quantity is greater with equal over-all bulb length. The method of manufacture is simplified and is cheaper because the difculties in the prior art lamp when sealing olf the short glass tip on the bulb dome and cooling with nitrogen are both omitted. A further reduction in production cost is obtained because the higher consumption in filling gas in the prior art lamp is decreased in the new lamp in View of the different and simpler lling process without exposure to heat and evaporation. In that the radical extremes in temperature difference in short lengths of the glass present in manufacture of the prior art lamp do not exist with manufacture of the new, thereby avoiding strains in and breakage of the glass, materially reduces that type of waste and loss. Finally it may be said that danger of accident becomes lower because of omitting the liquid nitrogen and because of the oxygen being more definitely conned.

Turning now to consideration of the lamp shown in FIGS. 5 and 5A, the upper dome end has not been shown since it is identical with the showing of FIGS. 2-4. The lower major portion 6a of the stern press or pinch is thicker than the showing in the former figures, and is laterally bifurcated part way upwardly for a distance from its lower end, thereby providing a bottom medial recess A establishing press legs 6a at the lateral sides of the recess and next to the lateral side edges of the press. At the transition between the bulb 5 and flattened press said press has duplicate and directly opposed transverse contractions 15 at the two broad faces of said press, thereby providing upwardly directed shoulders 15a.

symmetrically ldisposed `in-leads 13, 14 extend from below said legs 6a through the same and into bulb 5 to there carry the usual igniter. Between and longitudinally of said iu-leads there is located a small diameter thin-walled semi-hard copper tubulation 12 conforming to description of characteristics, treatment and installation of the tubulation 10 of FIGS. 2-4 except as to length, this tubulation 12 being shorter and terminating at its lower pinched end 11 within recess A. Accordingly, the pinched end 11 of the tubulation 12 provided in FIGS. 5 and 5A lies between press legs 6a and above the bottom plane thereof so that it is protected against mechanical injuries. This construction also is effective in keeping the end of the tubulation from 'being brought -into snagging contact with and possibly disturbing arrangement and construction of contacts in a lamp socket (not shown) wherein the lamp is ultimately used.

The press contractions 15 correspond to grooves b, b of the previously described construction and preferably have a corresponding distance between the contiguous contraction bottoms as provided between the groove bottoms for the same beneficial purpose of holding the lamp in a socket or magazine in use. The ends of the in-leads 13, 14 protruding from the bottoms of press legs 6a function as terminals for effecting electrical circuit connection with the socket contacts, and if applied against the same with a scraping engagement, a reliable electrical continuity will be assured.

In the construction shown in FIGS. 6 and 6A, the press 6b provides shoulders 15b at the lateral ends of the press and directed upwardly toward the bulb 5. The current in-leads 16, 17 are sealed throughthe press as in the above disclosures, but have a considerable length below the press, enabling said in-leads to be drawn tightly thereunder to a at side of the press, upwardly thereof to and `over said shoulder and bent to extend downwardly at the other flat side of the press, then entirely under the press this time and part way up the first flat side again. Thus, externally of the press, the in-leads are wrapped in tight loops, and if desired, grooves 18, 19 may be provided in the press surfaces for receiving the loops with a partial imbedding thereof. The loops are thus xed with respect to the press surfaces and have exposed portions protruding therefrom as lamp terminals for engagement with the socket contacts in use. Sealed within the press between the in-leads, there is located a small diameter thin walled semi-hard copper tubulation 12 conforming to description of characteristics, treatment and installation of the tubulation 1lb of FIGS. 2-4.

In the example shown in FIGS. 7 and 7A, each flat surface of the press 6c has an integral glass stud 15C, in effect constituting a shoulder, projecting outwardly therefrom. The stud on one side is near one lateral end of the press and the stud on the other side is near the other lateral end of the press. The in-leads 16C, 17C are sealed longitudinally through the press as last above described with excess of length therebelow enabling each to be drawn tightly under the press toward the side having the most proximate stud, then up to and over the stud and back down to pass under the press and. up at its other side. Thus again the in-leads of this showing, like those of the disclosure of FIGS. 6 and 6A, are wrapped in tight loops which function as lamp terminals for engage ment with the socket contacts in use. Also in this showing, as in the previous ones, there is sealed within the press between the in-leads, a small diameter thin walled semi-hard copper tubulation 12 conforming to description of characteristics, treatment and installation hereinbefore recited.

According to the showing in FIGS. 8 and 8A, a flattened press 6d is shown with directly opposed transverse grooves b b' and at an elevation corresponding to the location of said grooves, the in-leads 16C, 17C, intermediate of their length, are bent into U-shaped bows 16C and 17C' respectively. The bite portions of said bows are pushed through respective groove bottoms during the pinching process and being there exposed constitute lamp terminals for engagement with the socket contacts in use. In this instance, the bottom ends of the in-leads are not made to project below the bottom of the press. The positive retention of the bow with only the bite portion thereof protruding, obtains a very reliable fixation for the lamp contacts or terminals. As with previous showings, there is again here shown sealed within the press between the in-leads, a small diameter semi-hard copper tubulation 12 conforming to description of characteristics, treatment and installation hereinbefore recited.

In the example shown in FIGS. 9 and 9A, the thin walled semi-hard small copper tubulation 20, characterized as heretofore described, is used as one of the current in-leads. The other in-lead 21 is of usual wire and at its lower end projects beyond the flattened pinch or press and is looped over a boss 22 of glass integral with and protruding from the broad face of the press. The end of the inlead returns to the bottom of the pinch and into the same for anchoring thereof.

Finally, FIGS. 10 and 10A show an embodiment in which there are two small thin walled semi-hard copper tubulations 23 and 24 characterized as heretofore described, and which are sealed in the flattened pinch and serve as the current iii-leads. As viewed looking toward the narrow edge of the pinch, it will be seen that the pinch is formed with its mid-part bulging as at 25, by means of which good fixation in a resilient socket is guaranteed.

The seven different embodiments of flattened pinch shown in the drawings demonstrate that notwithstanding the use of presses or pinches of small dimensions, they will each one accommodate the small thin wal-led semi-hard copper tubulation without disturbing or hindering choice of shape of the base form or provision where desired of in-lead lamp terminals.

As hereinabove indicated, the pinch of the metallic tubulation may be doubly sealed, and illustrative of this feature, FIG. 11 shows a globule of coating 30 applied on the pinch 11 of tubulation 10. Then again, in FIG. 12, a coating 31 is shown covering the otherwise exposed portion of the tubulation as well as the pinch 11. The coating may comprise, in either showing, solder, rigid plastic, lacquer or other suitable material, either singly or as a laminated coating of different ones of said materials. In addition to doubly sealing the pinch 11, coatings 30 and 31 will also serve as protection and reenforcement for the thin-wall tubulation.

We claim:

1. A miniature lamp with a glass envelope and integral flattened press serving as the base, characterized in that pinched into the attened press in direct and permanently CII sealing contact with the glass thereof there is a thin-walled 3() tubulation of copper through which the lamp is lled with gas, said copper tubulation having a mechanical pinch near the place at which it cornes out of said attened press thereby providing a closure for said tubulation.

2. A miniature lamp as claimed in claim 1, characterized in that the glass envelope and its press through which said tubulation is sealed consists of a soft glass generally used for lamp purposes, as for instance lead glass and lime magnesia glass.

3. A miniature lamp as claimed in claim 1, characterized in that the thin-walled copper tubulation has an outer diameter within a limit of 1.5 mm and a wall thickness within a limit of 0.2 mm.

4. A miniature lamp as claimed in claim 3, characterized in that the thin-walled tubulation consists of semihard copper.

5. A miniature lamp as claimed in claim 1 characterized in that an external enwrapping reenforcing protective coating is applied to a portion of said tubulation yat least where the tubulation is mechanically pinched thereby doubly sealing and strengthening said tubulation thereat.

References Cited by the Examiner UNITED STATES PATENTS 2,280,048 4/ 1942 Schwarze 67-31 2,556,059 6/ 1951 Braunsdorff 316-20 X 2,914,371 11/ 1959 Wiedenmann 316--20 FOREIGN PATENTS 217,453 9/1958 Australia.

FREDERICK L. MATTESON, IR., Primary Examiner.

ROBERT A. DUA, Examiner. 

1. A MINIATURE LAMP WITH A GLASS ENVELOPE AND INTEGRAL FLATTENED PRESS SERVING AS THE BASE, CHRACTERIZED IN THAT PINCHED INTO THE FLATTENED PRESS IN DIRECT AND PERMANENTLY SEALING CONTACT WITH THE GLASS THEREOF THERE IS A THIN-WALLED TUBULATION OF COPPER THROUGH WHICH THE LAMP IS FILLED WITH GAS, SAID COPPER TUBULATION HAVING A MECHANICAL PINCH NEAR THE PLACE AT WHICH IT COMES OUT OF SAID FLATTENED PRESS THEREBY PROVIDING A CLOSURE FOR SAID TUBULATION. 